It's not a single Gang, but multiple gangs with different rules.
No other country in the world has a so granular and indipendent structure for it's police force.

Italy for example has:
Polizia di stato (State police)
Carabinieri (Gendarmerie, 4th armed force branch)
Guardia di finanza (Finance Minister police)
Guardia costiera (costal guards)

The minor forces, as regional, or local police, are generally cover only administrative role and are not always armed.